Multi-beam convergence controlling systems



prI 19, 1955 D. A. TANNENBAUM ETAL MULTI-BEAM CONVERGENCE CONTROLLING SYSTEMS Filed Maren 27, 1953 QS@ mwmh swnl l. Qwwmw United States Patent O F MULTI-BEAM CONVERGENCE CONTROLLING SYSTEMS Daniel A. Tannenbaum, West Collingswood, and Alton J. Torre, Woodbury, N. J., assignors to Radio Corporation of America, a corporation of Delaware Application March 27, 1953, Serial No. 344,924

13 Claims. (Cl. 315-13) This invention relates to systems for controlling the electron beam energy of cathode ray tubes. It pertains particularly to the control of a plurality of electron beam components used in television kinescopes so as to effect substantial convergence of the beam components at all points of a raster scanned in a predetermined lane.

p One type of cathode ray tube, in which there is encountered the problem of maintaining substantial convergence of a plurality of beam components in the plane of a target electrode, is a color kinescope such as that disclosed in a paper by H. B. Law titled A three-gun shadow-mask color kinescope published in the Proceedings of the IRE, vol. 39, No. 10, October 1951 at page 1186. Such a tube has a luminescent screen consisting of a multiplicity of phosphor areas of sub-elemental dimensions. Different ones of the phosphor areas are capable of producing light of the component image colors when excited by electron beam energy. In this tube, the diierent light-producing phosphor areas are excited respectively by a plurality of electron beams, or by a plurality of components of a single beam, approaching the screen from different angles through an apertured electrode. Color selection is secured by the angle at which the electron beam components approach the screen. A tube of the kind described forms the subject matter of U. S. Patent 2,595,548 granted May 6, 1952 to Alfred C. Schroeder for Picture Reproducing Apparatus.

The expression electron beam components as used in this specification and claims will be understood to denote the phosphor-exciting electronic energy produced either by a single, or by a plurality of, electron guns. This energy may be continuous or pulsating as required without departing from the scope of the invention. An example of a color kinescope in which different components of a single electron beam are used to excite a phosphor screen of the kind described 1s disclosed in a paper by R. R. Law, titled A one-gun shadowmask color kinescope published in the Proceedings of the IRE, vol. 39, No. l0, October 1951, at page 1194. Such a tube forms the subject matter of a copending U. S. patent application of Russell R. Law, Serial No. 165,552, led June l, 1950 and titled Color Television.

The successful operation of a multi-color kinescope of the type referred to requires that the plurality of electron beam components be made to converge substantially in the plane of the apertured electrode at all points in the scanned raster. In view of the fact that the different points of such a target electrode are at different distances from the point or region of the electron beam deflection, it is necessary to provide a fieldproducing means which is variably energized to produce the desired dynamic convergence control. One such electron beam control system is disclosed in a paper by Albert W. Friend titled Deflection and convergence in color kinescopes published in the Proceedings of the IRE, vol. 39, No. 10, October 1951 at page 1249. Such a system forms the subject matter of a copending P. S. patent application of Albert W. Friend, Serial No. 164,444, filed May 26, 1950 and titled Electron Beam Control System. In the system proposed by Friend, electron-optical apparatus is energized both statically and dynamically to produce the desired result. By means including the static energization of the electron-optical apparatus, the Friend system effects 1n- 2,706,796 Patented Apr. 19, 1955 ICC itial convergence of the electron beam components substantially at the center of the raster to be scanned. The dynamic energization of the electron-optical apparatus is effected as functions of both the horizontal and vertical beam deflections. Essentially these functions are parabolic. In the Friend and other systems previously employed, somewhat complicated apparatus has been required to produce the desired energizing waveforms.

Therefore, it is an object of this invention to provide improved and simplified apparatus by which to develop waveforms for the dynamic energization of an electron beam-controlling system for a multi-beam kinescope.

Another object of the invention is to provide irnproved apparatus by which to develop waveforms for effecting both static and dynamic convergence of the electron beam components of a multi-beam kinescope.

In accordance with this invention, there is provided apparatus by which to energize the field-producing means of a multi-beam cathode ray tube such as a tri-color kinescope of either of the types referred to by which to effect focusing and substantial convergence of a plurality of beam components at all points of a scanned raster. This apparatus comprises means, such as an electron tube, for linearly adding waves varying respectively at the horizontal and vertical deflection frequencies so as to produce in an output circuit separate convergence waves at the respective scanning frequencies. These waves then are combined in suitable proportions and impressed upon the field-producing means by which the focusing of the beam components is effected and also upon the field-producing means by which the convergence of the beam components is effected.

In accordance with a feature of the invention, the two waves at the respective horizontal and vertical frequencies are derived from the output circuits of the respective deflection apparatus. The output circuit of the Wave-combining tube includes two output transformers respectively responsive to the waves of different scanning frequencies. Corresponding terminals of the secondary windings of these output transformers are coupled to the beam convergence field-producing means and intermediate taps of these secondary windings are coupled to the beam-focusing field-producing means. In this manner, the beam convergence and beam-focusing field-producing means are energized respectively with waves of suitable form at both the horizontal and vertical deflection frequencies and in suitable proportional magnitudes to effect the desired results.

The novel features that are considered characteristic of this invention are set forth with particularty in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawing.

The single figure of the drawing is a general circuit diagram, partly in schematic and partly in block form, of television signal receiving apparatus embodying an illustrative form of the invention.

Reference now will be made to the drawing for a more detailed description of this illustrative embodiment of the invention. The television receiving apparatus represented in the drawing is generally conventional and includes an antenna 1 to which is coupled a conventional television receiver 2. It will be understood that the receiver 2 may include such usual apparatus as carrier wave amplifiers, at both video and intermediate frequencies, a frequency converter, and a carrier wave demodulator or signal detector. Accordingly, it will be understood that there is derived from the receiver 2 both the Video and synchronizing signals. The video signals derived from the receiver 2 are impressed upon a video signal channel 3, and the synchronizing signals are impressed upon a sync signal separator 4. The video signal channel, from which it will be assumed are derived the red, green and blue color representative signals R, G and B respectively, is coupled to the electron beam control apparatus, which customarily is referred to as the electron gun apparatus, of an image-reproducing device such as a kinescope 5.

In the illustrative embodiment of the invention shown in the drawing, it is assumed that the invention is to be used in a color television system. In such a case, the video signal channel 3 will necessarily include the proper apparatus to derive from the received television signal the different color represen-tative signals for the proper energization of the kinescope 5. inasmuch as such apparatus does not comprise any part of the present invention and, furthermore, is not necessary to an understanding of the invention, representative apparatus for deriving the different color representative signals is not disclosed so as to avoid undue complication of the drawing and the related description.

In a color television system, the kinescope 5 may be of the general type disclosed in the H. B. Law paper previously referred to. It will be understood, however, that the kinescope, alterna-tively, may be of other types such as that shown in the aforementioned R. R. Law paper. In either case, the kinescope has a substantially fiat luminescent screen 6 which is provided with a multiplicity of small phosphor areas arranged in groups and capable respectively of producing light of the different component colors in which the image is to be reproduced when excited by electron beam energy. In back of and spaced from the screen 6 there is an apertured masking electrode 7 which has an aperture for, and in alignment with, each group of phosphor areas of the screen 6.

In the particular tube illustrated, the kinescope 5 also has a plurality of diagrammatically represented electron guns 8, 9 and 10 equal in number to the number of component colors in which the image is to be reproduced. It will be understood that the color kinescope S may alternatively be provided with what, in effect, is a single electron gun having three separate apertures suitably placed to form three individual electron beams. As previously indicated, the three electron guns are coupled to the video signal channel 3 for respective control by video signals representing the three component colors in which the image is to be reproduced.

Also associated with the three electron guns are three corresponding individual beam-focusing anodes 11, 12 and 13. The three electron guns 8, 9 and 10, together with their associated focusing anode electrodes 11, 12 and 13, function to develop respective electron beams 14, 15 and 16 which are caused to approach the target electrode structure including the luminescent screen 6 and the masking electrode 7 from three different angles. For convenience in illustration, these angles have been shown in an exaggerated form in the drawing. By means of the different angles of approach, these beams are caused to excite the different color light-producing phosphors of the screen 6.

The kinescope also is provided with an electrostatic type of beam-converging apparatus which includes a convergence anode 17 located adjacent to the paths followed by the electron beams in the pre-defiection region. The kinescope also includes the usual final, or beam-accelerating, anode 18 which is generally in the form of a Wall coating subs-tantially as shown and extending from the pre-defiection region adjacent, to the convergence anode 12, to the vicinity of the target electrode structure including the screen 6. The electron lens formed by the convergence anode 17 and the final anode 18 is the fieldproducing means by which the desired convergence of the beams 14, 15 and 16 substantially in the plane of the masking electrode 7 is accomplished. It is the dynamic energization, as a function of beam defiection angle, of this field-producing electron-optical apparatus which effects the desired beam convergence at all points of the raster. Similarly, it is the dynamic energization as a function of beam deflection angle of the electronoptical lenses formed by the focusing anodes 11, 12 and 13 and the convergence anode 17 which insures that the individual beams are maintained in good focus throughout the entire raster scanned. It is the apparatus for effecting both the static and dynamic energization of the focusing and beam-converging apparatus which is the subject matter of the present invention and which will be described presently.

The color kinescope S also is provided with apparatus by which to defiect the plurality of electron beam components both vertically and horizontally to scan the usual raster at the luminescent screen 6. In this embodiment of the invention, the deflection apparatus includes a yoke 19 which, in general, may be of a conventional type. As such it consists of a pair of interconnected coils forming a horizontal defiection winding and another pair of coils forming a vertical deflection winding. The yoke is mounted around the neck of the kinescope in the region adjacent to the point at which the neck joins the conical section of the tube.

Horizontal and vertical windings of the yoke 19 are energized respectively by substantially conventional apparatus. The sync signal separator 4, which separates the horizontal and vertical sync signals from the video signals and also from one another, produces horizontal and vertical frequency sync signals respectively in its output circuits H and V. The horizontal output circuit H of the sync signal separator is coupled to a horizontal sweep oscillator 20, in the output of which a sawtooth wave 21 is produced. The output of the horizontal sweep oscillator is coupled to a horizontal output electron tube 22. Both of these horizon-tal sweep components may be entirely conventional. The anode of the horizontal output tube 22 is connected to a horizontal deflection output transformer 23. This transformer also is connected in a conventional manner to the horizontal deflection winding of the yoke 19.

The vertical sync separator output circuit V is coupled to a vertical sweep oscillator 24. This oscillator produces a substantially sawtooth wave Z5 at the vertical deiiection frequency. The output of the vertical sweep oscillator 24 is coupled to the input circuit of a vertical deflection output electron tube 26. The anode of this tube is coupled by means of a vertical deflection output transformer 27 to the vertical deflection winding of the yoke 19 in a substantially conventional manner.

In the following description of the remaining portion of the circuit embodying an illustrative form of the invention, reference will be made principally only to those circuit components which are closely associated with features of the invention and relate to its mode of operation. The other essential circuit components of a practical embodiment of the invention are shown with their proper connections and typical values thereof. In specifying the values of the circuit components it will be understood that all resistance values are given in ohms; all capacitance values which are less than 1.0 are to be understood as microfarads; and all capacitance values greater than 1.0 are to be understood as micromicrofarads, unless it is otherwise specified, as in a few instances where values above 1.0 are specifically designated as microfarads. It will be understood that in specifying resistance values, K is equivalent to 1000 ohms.

The cathode circuit of the horizontal output tube 22 includes a bypassed resistor forming an integrating network 28 by means of which the substantially sawtooth wave 21 is formed into a substantially parabolic wave 29 at the horizontal deflection frequency. Similarly, the cathode circuit of the vertical output tube 26 includes a bypassed vertical linearity controlling variable resistor forming an integrating network 31 by means of which the substantially sawtooth wave 25 is converted to a substantially parabolic wave 32 at the vertical deflection frequency.

By means including potentiometers 33 and 34, the horizontal and vertical substantially parabolic waves 29 and 32 respectively are impressed upon the input circuit of a convergence wave amplifier tube 35. This input circuit comprises the control grid of the tube and an impedance network including the series arrangement of a resistor 36 and a variable inductor 37. The vertical parabolic wave 32 is impressed upon one terminal of the resistor 36 and the horizontal parabolic wave 29 is impressed upon the other terminal of this resistor at its junction with the inductor 37 by means including a capacitor 38. The capacitor 38 in conjunction with the variable inductor 37 transforms the substantially parabolic horizontal wave 29 to a substantially sinusoidal wave 39 at the horizontal deflection frequency. The horizontal sinusoidal wave is additively combined with the vertical parabolic wave 32 in the input circuit of the convergence wave amplifier tube 35. The combined wave, therefore, has the general form of the wave 41 which is seen to be effectively a sine wave at horizontal deliection frequency which has a substantially parabolic envelope at the vertical deection frequency.

It has been found expedient to effect the dynamic control of convergence and beam focus at the horizontal deflection frequency by means of a sinusoidal wave rather than by one of parabolic form. It is much easier to develop, and to operate apparatus by, a sine wave than it is by a parabolic Wave. Furthermore, it has been found that, when using a parabolic wave at horizontal deflection frequency, the peak-to-peak value thereof, in order to effect the desired convergence, must be appreciably greater than the peak-to-peak value of a somewhat equivalent sine wave. Furthermore, the general shape of a sinusoidal Wave during the operative pictureproducin'g intervals closely enough approximates the shape of a parabolic wave to produce substantially the equivalent results. The use of a sinusoidal wave as .a substitute for a parabolic wave in effecting dynamic control of an electron beam convergence comprises the subject matter of a copending application of G. E. Kelly and R. D. Flood, Serial No. 198,314, filed November 30, 1950 and titled Electron Beam Convergence Systems."

The output circuit of the convergence wave amplifier tube 35 includes the anode of this tube and the serially connected primary windings of horizontal and vertical output transformers 42 and 43 respectively. A capacitor 44 is connected from the junction point between the primary windings 45 and 46, respectively, of the horizontal and vertical output transformers 42 and 43 to ground, thereby effectively shunting the vertical output transformer primary winding 46. By this means, the convergence wave energy produced in the output circuit of the amplifier tube 35 at horizontal deflection frequency is effectively bypassed around the vertical output transformer primary winding. At the same time, the capacitor 44 constitutes a relatively high impedance to the convergence wave energy in the output circuit of the tube 35 at vertical deflection frequency. The primary winding 45 of the horizontal output transformer 42 is tunable, as indicated, to the frequency of the horizontal sinusoidal wave 39. Accordingly, it is seen then that the substantially sinusoidal wave energy at horizontal deflection frequency produced in the output circuit of the tube 35 suitably energizes the primary winding 45 of the horizontal output transformer 42. Similarly, convergence wave energy at vertical deflection frequency energizes the primary winding 46 of the vertical output transformer 43.

Both of the horizontal and vertical output transformers 42 and 43 are constructed in a manner to effect a stepup in the voltage at the respective horizontal and vertical deflection frequencies. The horizontal output transformer 42, for example, has a prirnary-to-secondary turns ratio of 1 to 10, whereby the wave energy available at the terminals of the secondary winding 47 is approximately 3000 volts from peak-to-peak. The vertical output transformer 43 has a primary-to-secondary turns ratio of 1 to 6, whereby to produce at the terminals of the secondary winding 48 a vertical convergence wave having approximately a 1000 volt peak-t-peak` value.

A composite convergence wave including a substantially sinusoidal wave at horizontal deflection frequency and a substantially parabolic wave at vertical .deflection frequency is produced by coupling corresponding terminals of the secondary windings 47 and 48 together by means of a capacitor 49. This composite wave then is coupled by a capacitor 51 to the convergence anode 17 of the kinescope 5'. By such means, the potential which is impressed upon the convergence anode 17 is dynamically controlled at both horizontal and vertical deflection frequencies so as to vary the effectiveness of the electron-optical lens produced by the convergence anode and the nal anode 18. The static potential which is impressed upon the final anode 18 is derived in a conventional manner from a flyback type of power supply including a rectifier diode 52 connected to the horizontal deflection output transformer 23 so as to receive therefrom high voltage pulses developed during flyback, or retrace, intervals of the deflection apparatus. The static potential impressed upon the final anode 18 is maintained constant. Also, a static constant potential is impressed upon the convergence anode 17 by means including a potentiometer 53 included in a voltage divider, or bleeder network, connected across the high voltage power supply for the anode 18. The dynamic control of the convergence anode 17, whereby the effectiveness of electron-optical lens is varied to effect convergence, is-

provided in the manner described.

The secondary windings 47 and 48 of the horizontal and vertical output transformers 42 and 43, respectively,

also are provided with intermediate taps from which may be obtained sinusoidal and parabolic voltages at the horizontal and vertical deflection frequencies, respectively, of somewhat lower potential values than those produced at the terminals of these windings. These intermediate taps, preferably in accordance with the illustrative embodiment of the invention disclosed herein, are so placed that Waves having voltages approximately one-third of the maximum voltages produced at the terminals of the windings are obtained. These intermediate taps are coupled together by a capacitor 54 and also are coupled to the focusing anodes 11, 12 and 13 of the kinescope 5. In this manner, it is seen that the potential impressed upon these focusing anodes is dynamically controlled as a function of beam deflection so that it is proportional to the dynamic potential variation of the convergence anode 17. In this manner, the electron-optical lenses produced by the focusing anodes and the convergence anode are effective to maintain good beam focus throughout the scanned raster. It will be appreciated that, if the potentials impressed upon the focusing anodes 11, 12 and 13 were not varied dynamically as a function of beam deflection and the potential of the convergence anode 17 was varied in this manner, the electron-optical lenses produced by the focusing anodes and the convergence anode would be continuously changing with beam deflection angle, thereby varying the focusing effect upon the three individual beams. Such a feature of dynamic beam corivergence control forms the subject matter of a copending application of L. R. Kirkwood, Serial No. 198,313, filed November 30, 1950, now Patent No. 2,687,493, and titled Dynamic Electron Beam Control Systems, now Patent No. 2,687,493 issued August 24, 1954.

The static focusing potential which is impressed upon the anodes 11, 12 and 13 also is derived from a flyback type of power supply including a diode rectifier tube 55 which is coupled to the horizontal deflection output transformer 23 so as to receive high voltage pulses therefrom during flyback, or retract, intervals of the deflection apparatus. In this case, it is to be noted that, inasmuch as a considerably lower potential is required for impression upon the focusing anodes of the kinescope, the diode 55 is connected to a lower potential point on the winding of the horizontal deflection output transformer 23. The static focusing potential is derived from a potentiometer 56 included in a bleeder circuit across the flyback power supply including the tube 55. The potentiometer is connected to the common return point of the horizontal and vertical output transformer secondary windings 47 and 48. In this manner, it is seen that there is provided a direct means for impressing the dynamic focus control potential derived from the transformers 42 and 43 upon the static focusing voltage derived from the potentiometer 56 so that the two may be impressed together upon the focusing anodes 11, 12 and 13. It also is to be noted that this feature materially reduces the voltage rating requirement on the coupling capacitor 51. A static focusing potential of approximately 4 kilovolts is impressed upon the side of the capacitor 51 connected to the secondary winding 48 and a static convergence potential of approximately 11 kilovolts is impressed upon the other side of the capacitor which is connected to the convergence anode 17. Accordingly, it is seen that, instead of having to withstand a minimum of 1l kilovolts as in the case where one side of the coupling capacitor 51 is effectively grounded, it has only to withstand a potential of a minimum of 7 kilovolts with the present arrangement.

The general mode of operation of the apparatus embodying an illustrative form of the invention is considered to be clear from the foregoing description. Accordingly, further reference only will be made to a number of special operative features. The potentiometers 33 and 34 in the respective cathode circuits of the horizontal and vertical deflection output tubes 22 and 26 serve to control the respective amplitudes of the horizontal and vertical convergence waves produced ultimately in the secondary windings 47 and 48 on the horizontal and vertical output transformers 42 and 43, respectively. The horizontal sinusoidal wave, such as 39 and therefore the equivalent wave produced in the output transformers, is phased suitably relative to the horizontal deflection of the electron beams by means of the variable inductor 37. A somewhat equivalent function, which is more accurately described as shaping of the vertical parabolic wave, is effected by means of a' variable resistor S7 coupled between the anode and grid electrodes of the convergence wave grid amplifiers 3S. By such means, a feedback path is produced from the output to the input circuits of this tube. An adjustment of the resistor 57 changes the shape of the vertical parabolic wave by tilting it to one side or another of a symmetrical position. The feedback path provided by the circuit including the resistor 57 also serves to linearize the operation of the tube 35 so as to produce a more effective linear addition of the horizontal sinusoidal wave 39 and the vertical parabolic wave 32.

It is seen from the foregoing description of an illustrative embodiment of this invention that there is provided an improved and simplified apparatus by means of which to develop the necessary waveforms at both horizontal and vertical deflection frequencies for effecting the dynamic energization of an electron beam-controlling system for use with a multi-beam kinescope. Not only is the apparatus simple, requiring only a single electron tube for the amplification of the waveforms at the two different frequencies, but also the arrangement of the output transformers in such a way that they are respectively responsive to the waves of different frequencies constitutes an improvement over apparatus heretofore employed. A further feature of the present arrangement is the manner in which the static focusing potential is impressed upon the kinescope electrodes together with the dynamic potentials required for beam convergence. The several controls provided for adjusting the shapes and amplitudes of the different waves enables a more effective control of the apparatus.

The nature of the present invention having been set forth in the foregoing description of an illustrative embodiment thereof, its scope is set out in the appended claims.

What is claimed is:

l. In a cathode ray image-reproducing system wherein, a plurality of electron beam components, which traverse predeflection paths that are spaced respectively about the longitudinal axis of a tube are angularly deflected both horizontally and vertically to scan a raster in a predetermined plane and having field-producing means adjacent to said predeflection paths and energizable to effect focusing and substantial convergence of said beam components at all points of said raster, a system to energize said field-producing means comprising, horizontal and vertical substantially sawtooth deflection wave apparatus coupled to respective deflection output circuits and also producing substantially parabolic waves respectively at horizontal and vertical deflection frequencies, a convergence wave amplifier having an input circuit coupled to said horizontal and vertical deflection apparatus, means in said input circuit to effect a substantially linear addition of said convergence wave, an output circuit for said amplifier coupled to said field-producing means, and horizontal and vertical output transformers included in said output circuit and respectively responsive to said horizontal and vertical convergence waves.

2. In a cathode ray image-reproducing system wherein, a plurality of electron beam components which traverse predeflection paths that are spaced respectively about the longitudinal axis of a tube are angularly deflected both horizontally and vertically to scan a raster in a predetermined plane and having field-producing means adjacent to said predeflection paths and energizable to effect focusing and substantial convergence of said beam components at all points of said raster, a system to energize said field-producing means comprising, horizontal and vertical substantially sawtooth deflection wave apparatus coupled to respective deflection output circuits and also producing substantially parabolic waves respectively at horizontal and vertical deflection frequencies, means coupled to said horizontal deflection apparatus to transform said parabolic Wave to a substantially sinusoidal wave at the horizontal deflection frequency, a convergence wave amplifier tube having an input circuit including a control grid and an output circuit including an anode, horizontal and vertical output transformers respectively responsive to said horizontal sinusoidal and vertical parabolic waves coupled between said anode and said field-producing means, an imput impedance network connected to said grid, means coupling a terminal of said impedance network to said vertical deflection apparatus, and means coupling an intermediate point of said impedance 116twork to said horizontal deflection apparatus.

3. An energizing system for field-producing means as defined in claim 2 wherein, said impedance network includes a series arrangement of a resistor and an inductor, said vertical deflection apparatus being coupled to the terminal of said resistor, and said horizontal deflection apparatus being coupled to the junction point of said resistor and said inductor.

4. An energizing system for field-producing means as defined in claim 3 wherein, said horizontal deflection apparatus coupling means includes a capacitor forming a series circuit with said inductor tuned to said horizontal deflection frequency, thereby transforming said horizontal parabolic wave to a sinusoidal wave at horizontal deflection frequency.

5. An energizing system for field-producing means as defined in claim 4 wherein, said inductor is adjustable to control the phasing of said horizontal sinusoidal wave re1- ative to said horizontal beam deflection.

6. An energizing system for field-producing means as defined in claim 2 wherein, a feedback circuit is included between said anode and said grid.

7. An energizing system for field-producing means as defined in claim 6 wherein, said feedback circuit includes an adjustable resistor to vary the shaping of said vertical parabolic wave.

8. In a cathode ray image-reproducing system wherein a plurality of electron beam components which traverse predeflection paths that are spaced respectively about the longitudinal axis of a tube, are angularly deflected both horizontally and vertically to scan a raster in a predetermined plane and having field-producing means adjacent to said predeflection paths and energizable to effect focusing and substantial convergence of said beam co1:- ponents at all points of said raster, a system to energize said field-producing means comprising, horizontal and vertical substantially sawtooth deflection wave apparatus coupied to respective deflection output circuits and also producing substantially parabolic waves respectively at horizontal and vertical deflection frequencies, means coupled to said horizontal deflection apparatus to transform said parabolic wave to a substantially sinusoidal wave at the horizontal deflection frequency, a convergence wave amplifier tube having an input circuit coupled to said vertical deflection apparatus and to said horizontal wavetransforming means to effect a substantially linear addition of said vertical parabolic and said horizontal sinusoidal waves, said wave amplifier tube also having an output circuit, horizontal and vertical output transformers having respective primary windings serially connected in the output circuit of said wave amplifier tube and respectively responsive to said horizontal sinusoidal and said vertical parabolic waves, said output transformers also having respective secondary windings each having a tap intermediate of its terminals, means coupling corresponding terminals of said secondary windings to said fieldproducing means effecting convergence of said beam components, and means coupling the intermediate terminals of said secondary windings to said field-producing means effecting focusing of said beam components.

9. An energizing system for field-producing means as defined in claim 8 wherein, a capacitor connected effectively in shunt with the primary winding of said vertical output transformer renders said horizontal and vertical output transformers respectively unresponsive to said vertical parabolic and horizontal sinusoidal Waves.

10. An energization system for field-producing means as defined in claim 9 wherein, said horizontal output transformer primary winding is tunable to said horizontal deflection frequency.

l1. An energization system for field-producing means as defined in claim 8 wherein, the other corresponding terminals of said output transformer secondary windings are connected to a source of static focusing potential, and said coupling means to said convergence fieldproducing means includes a capacitor preventing the impression of said static focusing potential upon said convergence field-producing means.

l2. An energization system for field-producing means as defined in claim ll wherein, said convergence eldproducing means is connected to a source of static convergence potential.

13. ln a cathode ray image-reproducing system wherein, a plurality of electron beam components, which traverse deflection paths that are spaced respectively about the longitudinal axis of a tube, are angularly deflected both horizontally and vertically to scan a raster in a predetermined plane and having field-producing means adjacent to said predeflection paths and energizable to effect focusing and substantial convergence of said beam components at all points of said raster, a system to energize said fieldproducing means comprising horizontal and vertical substantially sawtooth wave apparatus coupled to respective deflection output circuits and also producing substantially parabolic waves respectively at horizontal and-vertical deflection frequencies, means coupled to said horizontal deflection apparatus to transform said parabolic wave to a substantially sinusoidal wave aty the horizontal deliection frequency, a convergence wave amplifier tube having au input circuit including a control grid and an output circuit including an anode, horizontal and vertical output transformers having respectively primary windings serially connected in the output circuit of said wave ampliiier tube, a capacitor connected effectively in shunt with the primary winding of said vertical output transformer, and the primary winding of said horizontal output transformer being tunable to said horizontal deflection frequency, whereby to render said horizontal and vertical output transformers respectively responsive to said hori zontal sinusoidal and said vertical parabolic waves, an input impedance network connected to said wave ampliiier grid and including a series arrangement of a resistor and a variable inductor, means coupling said vertical deflection apparatus to the terminal of said input circuit resistor, means including a capacitor forming a series tuned circuit with said input circuit inductor and coupling said horizontal deliection apparatus to the junction point of said resistor and said inductor and transforming said horizontal parabolic Wave to a sinusoidal wave at horizontal deflection frequency, a feedback circuit including an adjustable resistor connected between said wave ampliiier anode and grid to control the shaping of said vertical parabolic wave, said horizontal and vertical output transformers also having respective secondary windings each having a tap intermediate of its terminals, means coupling corresponding terminals of said secondary windings to said field-producing means effecting convergence of said beam components, means coupling the intermediate terminals of said secondary windings to said fieldproducing means effecting focusing of said beam components, means connecting the other corresponding terminals of said output transformer secondary windings to a source of static focusing potential, a blocking capacitor connected between said convergence field-producing means and said other terminal of said vertical output transformer to prevent the impression of said static focusing potential upon said convergence field-producing means, and means connecting said .convergence field-producing means to a source of static convergence potential.

References Cited in the le of this patent UNITED STATES PATENTS 2,338,646 Kessler Jan. 4, 1944 2,449,524 Witherby et al. Sept. 14, 1948 2,572,858 Harrison Oct. 30, 1951 

